Diffraction spikes very long?

[Orion_the_Hunter]

I was out with my scope a couple of nights ago (200p Dob), testing new 32mm Panaview.

When I was near to Sirius, I thought I could see very thin vapour trails. When I followed them, it became clear that they were light 'beams' from Sirius.

Is this normal? Collimation seemed ok on a star test.

Thanks.

[andrew s]

Yes quite normal, they are diffraction effects of the spider that holds the secondary mirror - Andrew

[Orion_the_Hunter]

Thanks Andrew.

Is it normal for them to stretch so far when the star is well out of the ep?

[Jannis]

When i image with my explorer 200pds and canon 550d, at long exposures, i have them all the way accross the image. So all normal i guess :-)

[andrew s]

Is it normal for them to stretch so far when the star is well out of the ep?

Yes as long as the star light can hits the spider it will create the diffraction pattern and if this extends into the field of view you will see it. Andrew

[Orion_the_Hunter]

Thanks